Make the default exclusion policy public

[elexx]

I need EasyRandom to ignore fields in superclasses.

Given the following classes (getter/setter for better readability omitted) ...

public abstract class BaseEntity {
    private long id;
    private int version;
}

public class User extends BaseEntity {
    private String name;
}

... I want EasyRandom to only fill the name when creating objects with easyRandom.nextObject(User.class).

I tried two different ways to implement this, but I'm not happy with either one of them:

// works but is not really futureproof. New superclasses must be added to the list
IGNORED_CLASSES =  Arrays.asList(BaseEntity.class);
...
    .excludeField(f -> !IGNORED_CLASSES.contains(field.getDeclaringClass()))

// works but it's a bit hacky imho.
// delegating to the original ExclusionPolicy instead of simply extending it, because
//    a) the default policy might change and
//    b) the original implementation is package-private: https://github.com/j-easy/easy-random/blob/master/easy-random-core/src/main/java/org/jeasy/random/ExclusionChecker.java
EasyRandomParameters parameters = new EasyRandomParameters();
ExclusionPolicy originalPolicy = parameters.getExclusionPolicy();
parameters.setExclusionPolicy(new ExclusionPolicy() {
    @Override
    public boolean shouldBeExcluded(Field field, RandomizerContext context) {
        return originalPolicy.shouldBeExcluded(field, context) || field.getDeclaringClass() == context.getCurrentObject().getClass();
    }

    @Override
    public boolean shouldBeExcluded(Class<?> type, RandomizerContext context) {
        return originalPolicy.shouldBeExcluded(type, context);
    }
});

Unfortunately using org.jeasy.random.annotation.Exclude is also not an option, because the superclasses actually live inside another library I have no control over.

[fmbenhassine]

Hi @elexx ,

Thank you for opening this issue!

delegating to the original ExclusionPolicy instead of simply extending it

I made ExclusionChecker public and renamed it to DefaultExclusionPolicy. You can now extend it with additional exclusion logic and register it in your config. Here is a quick test that shows how to exclude inherited fields based on your example:

public abstract class BaseEntity {
    protected Long id;
    protected Integer version;
}

public class User extends BaseEntity {
    private String name;
}

public class MyExclusionPolicy extends DefaultExclusionPolicy {
    @Override
    public boolean shouldBeExcluded(Field field, RandomizerContext context) {
        return super.shouldBeExcluded(field, context) || !field.getDeclaringClass().equals(context.getTargetType());
    }
}

@Test
void testInheritedFieldExclusion() {
    // given
    EasyRandomParameters parameters = new EasyRandomParameters()
            .exclusionPolicy(new MyExclusionPolicy());
    EasyRandom easyRandom = new EasyRandom(parameters);
    
    // when
    User user = easyRandom.nextObject(User.class);

    // then
    Assertions.assertThat(user.name).isNotNull();
    Assertions.assertThat(user.id).isNull();
    Assertions.assertThat(user.version).isNull();
}

This test passes with 4.2.0-SNAPSHOT and the change will be part of the upcoming 4.2 release. Feel free to give it a try and share your feedback!